About six years ago, I learned the Doomsday algorithm for computing dates, which relies on the fact that the last day of February, 4/4, 6/6, 8/8, 10/10, and 12/12 all fall on the same day of the week every year. Which day of the week this is is called the Doomsday for that year. Unfortunately, I do not have such a technique for easily recalling these Doomsdays, so I rely on a bit of calculation. My current strategy is as follows:

Use your left hand (or right hand if you’re like me and lefthanded) and assign the fingers from Monday to Friday. Saturday and Sunday will be the gaps on either side  a “missing finger” if you will.

For 1900, start on Wednesday. For 2000, start on Tuesday.

Add 28 repeatedly  28, 56, 84 (e.g. 1928, 1956…). You don’t move your finger during this calculation. Stop before you overflow (go past the year you want).

Add 4 repeatedly, moving back two fingers every time you do so. Again, stop before you overflow.

Add 1 for each year after that, moving forward one finger each time until you reach your desired year. The result will be the Doomsday.
For example, 1983. I would start on Wednesday for 1900, 1928, 1956, and move back twelve fingers until 1980, and move forward three for 1983. The result of the calculation is a Monday Doomsday, but it takes me about 5 seconds to compute this rapidly. From there, I have to calculate the month and day, which in a worstcase scenario is another 5 seconds. The finger I end up on is the result for that day.
Also, I don’t want to have to rely on a physical method for determining the day of the week. I wish I could do it mentally, and faster. (For calculating a calendar day this year for example  I still have to calculate the Doomsday for the year! 2000, 2004, 2008, 2012, 2016, 17, 18, 19… it’s Thursday. October 10 is Thursday, so calculate from there.)
I wonder if there’s an easier method. What am I doing that’s inefficient? Could I reduce the problem to a list of codes or a memory palace, placing all of the Tuesdays together or trying to link 19 (a roll of tape in my Major system) to 4 (Thursday  FOURSday, I start from 1 on Monday)?
Hmmm…